Sulfides (also called thioethers) are prepared by the efficient SN2 reaction of primary or secondary haloalkanes with a thiolate anion (RS-). This is an SN2 reaction and is subject to the usual limitations, although thiolate anions are excellent nucleophiles but modest bases. Thiols are easily deprotonated by modest bases such as potassium carbonate (K2CO3), so thiolate anions are generally generated within the reaction (Section 7.3A).